1. Field of Invention
This invention relates generally to apparatus and methods for measuring the presence of ionic matter, and particularly to a self-purging deionization apparatus and method for determining the quantitative presence of derived ions from various items where ionic content may be critical.
2. Description of Prior Art
Electronic circuits and electronic components may be impaired by environmental conditions. They are usually shielded from them by some form of protective packaging. However, the presence of ionic contamination residues of processing on the surface of printed circuit boards and components constitutes a danger for which environmental shielding is no protection. Ionic contamination of the surface of printed circuit boards and components may seriously impair reliability and stability. Electrical leakage and corrosion of metallic elements may result. In spite of attempts to provide the highest level of cleanliness, and indeed the purging of electronic circuits and components with suitable solvents, the final circuit assembly may have traces of ionic contamination resulting from prior processing such as plating, etching, handling, fluxing, soldering or the deposition of air-borne contaminants. Bathing electronic circuits and components after fluxing and soldering may not be effective. The use of trichloroethylene, isopropanol, deionized water, or acetone followed by drying may not be completely effective. Certain fluxes are not soluble in water and may erect a protective shield over ionic soils and residues preventing their removal. The essential removal of ionic soils may thus be uncertain.
It is an object of the present invention to provide a very sensitive means for determining the presence of soils on electronic circuits and components. Another object of this invention is to provide a means for quantitatively determining the presence of ionizable material on electronic circuits or components; yet another object of the invention is to provide a means for determining the rate of ionic soil removal from an item; a further object of the invention is to provide a means for determining the ionic contamination of electronic circuits and components, which means will not itself impart contamination to the item being tested. Another object of the invention is to provide a permanent record of the rate and degree of removal of ionic soils from electronic circuits and components.
There are numerous other situations where solids carry ionic material which may even be desirable, but in any event, requires evaluation. The same thing is true of liquids (e.g. preparation of pharmaceutical compounds; ultra pure water for nuclear reactors) and gases (e.g. biology: to measure byproducts of metabolism; ecology: measure levels of sulphur dioxide in the air).